[PCB_FORUM] Re: Power plane -vs- gnd path signal return path

From my limited understanding, your assumption is correct and the key
is achieving the correct (capacitive) coupling between the planes.

Jim Wages wrote:

Ok, folks. Let me know if my thinking is wrong here.
I have a 14 layer stack up. External etch layers are adjacent to power planes, which are adjacent to ground planes. Lyr 2 is a split power plane. Lyr13 is a solid 3.3V plane.
Do you see any signal "return path" or integrity issues with routing a critical signal trace on the bottom layer as long as the driver of the signal was powered by 3.3V. What about a differential pair?
I'm assuming that the power and gnd planes would be perceived as a short to hi-frequency signals, so that the return path would not have to get to a ground plane, but would just stay on the 3.3V plane directly beneath the trace until it returned to the driver. 

Thoughts?


*//**/Jim S. Wages/*

*SR. PCB Layout Designer*


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